The present invention relates to an antenna device for direction finders which has a plurality of antenna elements and a switching circuit for rotating the directivity of the antenna device.
Where an antenna placed horizontally above ground has one end grounded with the other end used to produce a received output signal, the antenna exhibits sensitivity characteristics in the pattern of a cardioid diagram as the direction in which a wave arrives varies. Such an antenna may be employed to provide a direction finder. However, conventional directional finders have been complex in arrangement since it has been necessary to rotate the antenna mechanically or provide a number of antennas oriented in various directions, and to compare output signals from such antennas.